Treating heart disease with foxgloves

The common foxglove (Digitalis purpurea) is a pretty flower native to Western Europe. It is commonly found in open spaces especially in recently cleared woodland and other places where the ground has been disturbed, but is also popular in gardens as an ornamental plant (1). Although the plant is poisonous to eat, it has been used in traditional medicines for centuries, but it wasn’t until the 18th century that its medicinal benefits were thoroughly examined by a British doctor called William Withering (2).

Dropsy (now known as oedema) is the build up of fluid in the body. In the 18th century the condition was often fatal as patients could “drown” in the fluid that built up in their lungs. Dropsy can be caused by heart failure because the decreased flow of blood around the body leads to the kidneys retaining more fluid.

William Withering became interested in using foxgloves to a cure dropsy after talking to Mother Hutton, a herbalist from Shropshire (3). Withering spent almost 10 years studying the plant and found that the active ingredient – known as digitalis – could be an effective treatment for dropsy because it slows down and strengthens the heart beat. He published his findings in 1785 in a landmark paper that was the first English text to describe the therapeutic effects of a drug (1).

The drug digitalis is made of two compounds called digitoxin and digoxin (4). These compounds work by inhibiting a pump protein that moves sodium ions out of heart muscle cells in exchange for moving potassium ions into the cells. This alters the balance of ions in the heart cells, which slows down the heart beat and increases the force of contraction of the cells. Too high a dose of digitalis can cause the heart to stop beating, which is why foxgloves are poisonous to eat.

Today, digitalis is extracted from the woolly foxglove (Digitalis lanata) (5). It is widely used to treat irregular heart rhythms and sometimes to treat heart failure if other drugs have failed. However, its use is declining as more effective drugs become available.

The heyday of digitalis as a treatment for heart disease may be over but recent studies suggest that the drug can selectively target cancer cells and limit their growth. Therefore, it is possible that digitalis could be used to treat cancer.

The common foxglove (Digitalis purpurea) is the Organism of March here at Plant Scientist.